Escherichia coli, Haemophilus spp. and Campylobacter spp. all produce
a toxin that is seen to cause distension in certain cell lines [1,2],
which eventually disintegrate and die. This novel toxin, termed cytolethal
distending toxin (cdt), has three subunits: A, B, and C. Their sizes are
approx. 27.7, 29.5 and 19.9kDa respectively [1], and they appear to be
entirely novel [2].
Further research on the complete toxin has revealed that it blocks the cell
cycle at stage G2, through inactivation of the cyclin-dependent kinase Cdk1
[3], and without induction of DNA breaks. This leads to multipolar abortive
mitosis and micronucleation, associated with centrosomal amplification [3].
The roles of each subunit are unclear, but it is believed that they have
separate roles in pathogenicity.
CDTOXINC is a 5-element fingerprint that provides a signature for cytolethal
distending toxin C proteins. The fingerprint was derived from an initial
alignment of 2 sequences: the motifs were drawn from conserved regions
spanning the full alignment length (~160 amino acids). Two iterations on
SPTR37_10f were required to reach convergence, at which point a true set
comprising 3 sequences was identified.